> On Sep 19, 2015, at 9:14 PM, Gideon Simpson <[email protected]> wrote: > > Yes, I know exactly where the zero diagonal entries are. Is there a way to > compensate for that?
Not really. How can you update x_i if A_ii = 0 ? > > -gideon > >> On Sep 19, 2015, at 10:09 PM, Barry Smith <[email protected]> wrote: >> >> >> Oh, it is a different kind of zero pivot value. There is a zero on the >> diagonal while it is trying to do SOR. Should there be zeros on the >> diagonal of your matrix? >> >> You can use -mg_levels_pc_type jacobi and it will ignore those zero >> values. >> >> Barry >> >> >>> On Sep 19, 2015, at 7:12 PM, Gideon Simpson <[email protected]> >>> wrote: >>> >>> I never get to see the output. When it runs, I get: >>> >>> 0 SNES Function norm 8.405398322914e-02 >>> [0]PETSC ERROR: --------------------- Error Message >>> -------------------------------------------------------------- >>> [0]PETSC ERROR: Zero pivot in LU factorization: >>> http://www.mcs.anl.gov/petsc/documentation/faq.html#zeropivot >>> [0]PETSC ERROR: Zero pivot on row 0 >>> [0]PETSC ERROR: See http://www.mcs.anl.gov/petsc/documentation/faq.html for >>> trouble shooting. >>> [0]PETSC ERROR: Petsc Release Version 3.6.1, unknown >>> [0]PETSC ERROR: ./blowup_refine on a arch-darwin-c-debug named gs_air by >>> gideon Sat Sep 19 20:11:44 2015 >>> [0]PETSC ERROR: Configure options --download-mpich=yes >>> --download-suitesparse=yes --download-superlu=yes >>> --download-superlu_dist=yes --download-mumps=yes --download-sprng=yes >>> --with-cxx=clang++ --with-cc=clang --with-fc=gfortran --download-metis=yes >>> --download-parmetis=yes --download-scalapack=yes >>> [0]PETSC ERROR: #1 MatSOR_SeqAIJ_Inode() line 2795 in >>> /opt/petsc/src/mat/impls/aij/seq/inode.c >>> [0]PETSC ERROR: #2 MatSOR_MPIAIJ() line 1496 in >>> /opt/petsc/src/mat/impls/aij/mpi/mpiaij.c >>> [0]PETSC ERROR: #3 MatSOR() line 3697 in >>> /opt/petsc/src/mat/interface/matrix.c >>> [0]PETSC ERROR: #4 PCApply_SOR() line 37 in >>> /opt/petsc/src/ksp/pc/impls/sor/sor.c >>> [0]PETSC ERROR: #5 PCApply() line 483 in >>> /opt/petsc/src/ksp/pc/interface/precon.c >>> [0]PETSC ERROR: #6 KSP_PCApply() line 242 in >>> /opt/petsc/include/petsc/private/kspimpl.h >>> [0]PETSC ERROR: #7 KSPInitialResidual() line 63 in >>> /opt/petsc/src/ksp/ksp/interface/itres.c >>> [0]PETSC ERROR: #8 KSPSolve_GMRES() line 235 in >>> /opt/petsc/src/ksp/ksp/impls/gmres/gmres.c >>> [0]PETSC ERROR: #9 KSPSolve() line 604 in >>> /opt/petsc/src/ksp/ksp/interface/itfunc.c >>> [0]PETSC ERROR: #10 KSPSolve_Chebyshev() line 381 in >>> /opt/petsc/src/ksp/ksp/impls/cheby/cheby.c >>> [0]PETSC ERROR: #11 KSPSolve() line 604 in >>> /opt/petsc/src/ksp/ksp/interface/itfunc.c >>> [0]PETSC ERROR: #12 PCMGMCycle_Private() line 19 in >>> /opt/petsc/src/ksp/pc/impls/mg/mg.c >>> [0]PETSC ERROR: #13 PCApply_MG() line 340 in >>> /opt/petsc/src/ksp/pc/impls/mg/mg.c >>> [0]PETSC ERROR: #14 PCApply() line 483 in >>> /opt/petsc/src/ksp/pc/interface/precon.c >>> [0]PETSC ERROR: #15 KSP_PCApply() line 242 in >>> /opt/petsc/include/petsc/private/kspimpl.h >>> [0]PETSC ERROR: #16 KSPInitialResidual() line 63 in >>> /opt/petsc/src/ksp/ksp/interface/itres.c >>> [0]PETSC ERROR: #17 KSPSolve_GMRES() line 235 in >>> /opt/petsc/src/ksp/ksp/impls/gmres/gmres.c >>> [0]PETSC ERROR: #18 KSPSolve() line 604 in >>> /opt/petsc/src/ksp/ksp/interface/itfunc.c >>> [0]PETSC ERROR: #19 SNESSolve_NEWTONLS() line 233 in >>> /opt/petsc/src/snes/impls/ls/ls.c >>> [0]PETSC ERROR: #20 SNESSolve() line 3906 in >>> /opt/petsc/src/snes/interface/snes.c >>> [1]PETSC ERROR: #1 VecNorm_MPI() line 63 in >>> /opt/petsc/src/vec/vec/impls/mpi/pvec2.c >>> [1]PETSC ERROR: #2 VecNorm() line 242 in >>> /opt/petsc/src/vec/vec/interface/rvector.c >>> [1]PETSC ERROR: #3 VecNormalize() line 337 in >>> /opt/petsc/src/vec/vec/interface/rvector.c >>> [1]PETSC ERROR: #4 KSPGMRESCycle() line 127 in >>> /opt/petsc/src/ksp/ksp/impls/gmres/gmres.c >>> [1]PETSC ERROR: #5 KSPSolve_GMRES() line 236 in >>> /opt/petsc/src/ksp/ksp/impls/gmres/gmres.c >>> [1]PETSC ERROR: #6 KSPSolve() line 604 in >>> /opt/petsc/src/ksp/ksp/interface/itfunc.c >>> [1]PETSC ERROR: #7 KSPSolve_Chebyshev() line 381 in >>> /opt/petsc/src/ksp/ksp/impls/cheby/cheby.c >>> [1]PETSC ERROR: #8 KSPSolve() line 604 in >>> /opt/petsc/src/ksp/ksp/interface/itfunc.c >>> [1]PETSC ERROR: #9 PCMGMCycle_Private() line 19 in >>> /opt/petsc/src/ksp/pc/impls/mg/mg.c >>> [1]PETSC ERROR: #10 PCApply_MG() line 340 in >>> /opt/petsc/src/ksp/pc/impls/mg/mg.c >>> [1]PETSC ERROR: #11 PCApply() line 483 in >>> /opt/petsc/src/ksp/pc/interface/precon.c >>> [1]PETSC ERROR: #12 KSP_PCApply() line 242 in >>> /opt/petsc/include/petsc/private/kspimpl.h >>> [1]PETSC ERROR: #13 KSPInitialResidual() line 63 in >>> /opt/petsc/src/ksp/ksp/interface/itres.c >>> [1]PETSC ERROR: #14 KSPSolve_GMRES() line 235 in >>> /opt/petsc/src/ksp/ksp/impls/gmres/gmres.c >>> [1]PETSC ERROR: #15 KSPSolve() line 604 in >>> /opt/petsc/src/ksp/ksp/interface/itfunc.c >>> [1]PETSC ERROR: #16 SNESSolve_NEWTONLS() line 233 in >>> /opt/petsc/src/snes/impls/ls/ls.c >>> [1]PETSC ERROR: #17 SNESSolve() line 3906 in >>> /opt/petsc/src/snes/interface/snes.c >>> >>> and then it just sits there. >>> >>> -gideon >>> >>>> On Sep 19, 2015, at 7:18 PM, Matthew Knepley <[email protected]> wrote: >>>> >>>> On Sat, Sep 19, 2015 at 6:10 PM, Gideon Simpson <[email protected]> >>>> wrote: >>>> It gives zero pivots on: >>>> >>>> Send -ksp_view >>>> >>>> Matt >>>> >>>> -ksp_type gmres -pc_type gamg -mg_coarse_sub_pc_factor_shift_type NONZERO >>>> >>>> It has no problem with: >>>> >>>> -ksp_type gmres -pc_type bjacobi -sub_pc_factor_shift_type NONZERO >>>> >>>> -gideon >>>> >>>>> On Sep 19, 2015, at 12:37 AM, Barry Smith <[email protected]> wrote: >>>>> >>>>> >>>>>> On Sep 18, 2015, at 10:42 PM, Gideon Simpson <[email protected]> >>>>>> wrote: >>>>>> >>>>>> I’m getting a zero pivot in LU factorization error when I use the gamg >>>>>> preconditioner. I know there is some issue with my matrix, as I get the >>>>>> same error if I use pc_type lu in serial, or if I use pc_type bjacobi in >>>>>> parallel, both of which are corrected by adding -pc_factor_shift_type >>>>>> NONZERO -sub_pc_factor_shift_type NONZERO, respectively. However, I >>>>>> can’t quite seem to figure out the analogous command to use for the gamg >>>>>> preconditioner. >>>>> >>>>> You need to figure out the prefix to the option that is added by gamg to >>>>> set it. One way is to run with the gamg options and -help and grep for >>>>> factor_shift. >>>>> >>>>> The option is like something like -mg_coarse_pc_factor_shift_type >>>>> nonzero or -mg_coarse_sub_pc_factor_shift_type >>>>> >>>>> Barry >>>>> >>>>>> >>>>>> -gideon >>>>>> >>>>> >>>> >>>> >>>> >>>> >>>> -- >>>> What most experimenters take for granted before they begin their >>>> experiments is infinitely more interesting than any results to which their >>>> experiments lead. >>>> -- Norbert Wiener >>> >> >
